Expression of caveolin-1 and polarized formation of invaginated caveolae in Caco-2 and MDCK II cells.
We have studied caveolin-1 expression and the frequency and distribution of typical invaginated caveolae as they are identified by electron microscopy in the polarized epithelial cell lines MDCK II and Caco-2. In wild-type MDCK II cells caveolin expression is high and more than 400 caveolae/mm filter were observed at the basolateral membrane. No caveolae were found at the apical surface. By contrast, wild-type Caco-2 cells do not express caveolin-1 and have extremely few, if any caveolae. Caco-2 cells were stably transfected with the gene for caveolin-1 in order to investigate if the formation of caveolae is polarized also in these cells. We have isolated Caco-2 clones expressing different levels of caveolin-1, where the level of expression varies from 10-100% of the endogenous level in MDCK II cells. Caveolin-1 expression in Caco-2 cells gives rise to a marked immunofluorescense labeling mainly at the lateral plasma membrane. By electron microscopy an increase from less than 4 caveolae/mm filter in wild-type Caco-2 cells to 21-76 caveolae/mm filter in Caco-2 clones transfected with caveolin-1 was revealed and these caveolae were exclusively localized to the basolateral membrane. Thus expression of heterologous caveolin-1 in Caco-2 cells leads to polarized formation of caveolae, but there is a lack of correlation between the amount of caveolin expressed in the cells and the number of caveolae, suggesting that factors in addition to caveolin are required for generation of caveolae.
Vogel
U
U
Structural Cell Biology Unit, Department of Medical Anatomy, The Panum Institute, DK-2200 Copenhagen N, Denmark.
Sandvig
K
K
van Deurs
B
B
D000818:Animals; D015153:Blotting, Western; D018938:Caco-2 Cells; D051242:Caveolin 1; D022461:Caveolins; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D004285:Dogs; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007668:Kidney; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry; D008854:Microscopy, Electron; D014162:Transfection
C495540:CAV1 protein, human; D051242:Caveolin 1; D022461:Caveolins; D008565:Membrane Proteins